In Missy's case she had been tearing up a shirt and part of the fibers got down her throat. She started coughing and thorwing up white goo. After some water and rest she was better, but I learned my lesson.

It sounds like when Leonard got Kennal Cough, when Leonard got it, it sounded like he was choking , he would cough a few times and then some mucas, a few times I thought he was puking...he had little appetite and was super tired....he got over it in a bout a week.

When we went through a pretty tenacious round of kennel cough with Abbie Lou, she would gag (sounded like she had something caught in her throat and was trying to harf it up), and there was some white frothy ejecta after some of those gaggy coughs. Her attitude/energy level was normal through all of it, really, she only seemed miserable when she was actually coughing.

Can you borrow a neighbor's phone or get to a pay phone to call the vet back? It could just be kennel cough...or it could be more serious. Sounds like the dog needs to see a vet as soon as you can get in.